1. Field of the Invention
The present invention relates to a digital signal processing apparatus which digitally processes analog signals, and more particularly to a digital signal processing apparatus for performing signal processing including orthogonal transform such as wavelet transform.
This application is based on Japanese Patent Application No. 9-001431, filed Jan. 8, 1997, the content of which is incorporated by reference.
2. Discussion of Background
So-called wavelet transform, which is a signal processing technique based on the wavelet theory, has been developed by combining short-time Fourier transform and matched filtering. Wavelet transform is defined by a mathematical formula, which is applied in many fields of technology. Various types of signal processing apparatuses which perform wavelet transform have been developed. Among them are:
1. An apparatus in which a DSP (Digital Signal Processor) performs wavelet transform by using a program describing the wavelet transform formula. PA1 2. An apparatus in which continuous wavelet transform is performed by utilizing an optical phenomenon, thereby extracting spectra, and a neutral network determines the feature of the phenomenon from the extracted spectra. PA1 3. An apparatus in which the wavelet transform formula is converted to binary data, and a digital circuit processes the binary data.
Of these signal processing apparatuses, the apparatus 1 is the most simple. An example of the apparatus 3, wherein wavelet transform is applied to image compression/expansion, is disclosed in U.S. Pat. No. 5,355,510 by the inventor of the present application.
The apparatus 1 executes a number of instructions, one by one, in order to achieve wavelet transform, and a great deal of time is therefore required to process signals. The apparatus 2 needs to have optical elements and is inevitably large in size. The apparatus 3 requires large-scale hardware to perform wavelet transform.
The conventional signal processing apparatuses which perform wavelet transform are disadvantageous in two respects. First, they are large in size. Second, they cannot perform wavelet transform at high speed.